If you hear the clicking/ticking sound that is the head moving back and forth trying to read information from the drive. At some point it may "give up" and skip ahead and be able to find a readable part of the hard drive again. I assume that it did this when you were watching a recording or pausing live TV as it shouldn't "freeze" when simply watching live TV, although you may hear the clicking/ticking as that live programme is always being recorded.
In terms of which drive to purchase, see the last few posts in the thread link I already provided. The "Purple" or "Black" WD drives are typically best for this application. Canada Computers is one place to purchase, although there are others. The iHDD replacement process is not for technophobes, but can be done by patient, skilled amateurs.
You mention WHPVR. I have the following comments/questions.
1. Is this the only PVR in your WHPVR setup?
2. If you have another PVR you could use that for your recordings and access them from this PVR and the other boxes in your setup.
3. When you encounter the problem are you viewing the PVR directly or via another box in another location in the home?
4. Did you check your signal strength yourself?
5. Since the PVR has been part of WHPVR and since these PVRs are now about 6 years old, it's certainly very possible that the iHDD is failing. Many start to fail around 3-5 years with hard use.
6. You could consider purchasing another used 9865 from someplace like Kijiji, but who knows how well that will work out. If you decide to go that route, read the tips in the following post:
https://www.digitalhome.ca/forum/37-rogers-cable-tv/64632-guidelines-selling-buying-used-rogers-terminal-ontario.html
You could consider switching to IgniteTV, but read the threads on IgniteTV in this forum first as some people have some issues...